Lever a lighter between the cap and your hand
This college party trick is more academic than it looks, bro: to get it to work properly, you are essentially creating a lever out of the lighter, using your knuckle as the fulcrum. Grip the neck of the bottle with your non-dominant hand, leaving a lighter’s-width of space between your top finger and the beer cap. Lay the broad side of the lighter against the largest knuckle of your top finger, with the lighter’s butt resting just under the cap. Apply downward force to the free end of the lighter, levering the other end upward against the cap. It should pop off in seconds. Once you master the mechanics of this lever trick, you can use pretty much any object as a stand-in for the lighter, including…
Lever a spoon between the cap and your hand
Using the same lever physics as the lighter method, you can almost effortlessly pop a cap with a common kitchen spoon (and not have to rely on the kindness of smokers to do it). Grip the bottle tightly with your non-dominant hand as explained above, then lay the curved side of the spoon against your largest knuckle, wedging the spoon’s small tip under the cap. Press downward on the spoon handle to lever the cap off lickety-split.